Harbaugh gives intruder the stare

Among the 32,000 fans who watched the 49ers practice at Candlestick Park on Sunday was one shirtless, middle-aged man who ran onto the field, sporting an ear-to-ear smile, before he appeared to sober up in midstride.

The reason: He was a few feet away from Jim Harbaugh.

The coach and fan had a brief staredown – the man held his arm up in surrender – before he was tackled by security.

“He and Harbaugh kind of had a moment there,” left tackle Joe Staley said. “They kind of locked eyes and Harbaugh withdrew him. He made him withdraw with his Chuck Norris eyes.”

Said Harbaugh: “Glad he was clothed. Glad he wasn’t naked.”

The attendance for the Fan Fest practice dwarfed last year’s total of 8,200. A large contingent stayed until the end of the 2 1/2-hour session and circled the field to get autographs. Harbaugh signed for about 30 minutes before speaking with reporters.

“The fan base here is really into the San Francisco 49ers,” safety Donte Whitner said. “They really care about the team and they want to see us get back to where we were in the ’80s and in the ’90s.”

Walker hurts knee: Tight end Delanie Walker fell to the ground and clutched his knee while blocking during practice, but Harbaugh suggested the injury isn’t serious.

“We’ll wait until we get some further results from the doctors, but I think we dodged another bullet there,” he said.

After being examined by trainers on the field for about five minutes, Walker walked very slowly to the sideline without assistance. A brace was later placed on his knee, which remained elevated during the rest of practice.

Aldon Smith outlook: Aldon Smith’s hip injury won’t keep the second-year outside linebacker out for an extended period of time. He was injured in the first quarter of Friday’s preseason opener. Harbaugh said Smith would miss “maybe a week or so.”